The force generated by hitting a baseball with a baseball bat may be quite large. Forces up to 8,000 to 9,000 pounds per square inch are not uncommon, especially with a fast-pitched baseball. Such potential high forces present safety concerns. A wooden bat may fracture during normal use, typically along a grain boundary, resulting in a sharply pointed projectile, which may be dangerous to both players and spectators.
Metal bats are also used in baseball. While the metal bats may not suffer from the potential fracture failure common with the wooden bats, metal bats may generate greater ball velocity off the bat, making the game of baseball more dangerous, especially for young or non-professional infielders, including pitchers. Some leagues and municipalities have even legislated against the use of metal bats in youth or scholastic sports, in an attempt to avoid potential injury.
Wooden bats have been reinforced to improve performance, including safety, strength or resistance against fracture. For example, U.S. Pat. No. 5,165,686 to Morgan describes the use of a rod of flexible plastic shaft centrally disposed within a wooden bat and extending throughout at least the handle section of the wooden bat to improve bat strength. U.S. Pat. No. 4,572,508 to You described a composite bat made from several wooden laminations with plastic layers disposed between the laminations to provide increase bat strength. U.S. Pat. No. 5,904,803 to Hillerich, III et al. describes a reinforced wooden baseball bat having a sleeve of braided fiberglass adhesively disposed over the entire exterior surface of a wooden bat. The wooden bat has longitudinally extending grooves which are described as being useful for providing the adhesive securement of the braided fiberglass sleeve to the wooden. U.S. Pat. No. 6,139,451 to Hillerich, III et al. attempts to improve adhesive securement of the fiberglass sleeve of the '803 patent, especially at the barrel portion of the bat, by providing a series of circular grooves at the barrel of the bat. The circular grooves are described as conduits for allowing air to escape from the longitudinal grooves as the adhesive is introduced into the longitudinal grooves. Such a composite bat, i.e., wooden core with a fiberglass outer sleeve, is commercially available as Louisville Slugger® Composite Bat TPXC271. Some of the composite bats, however, are not widely accepted in organized baseball leagues as the composite materials may alter the functionality of the wooden bat. In other words, while the prior art may have introduced reinforcement members to wooden bats, the resulting performance of the bat is altered as compared to the performance of a non-composite wooden bat.
The reinforced wooden bats of the prior art typically involve substantial use of non-wooden materials, including interiorly and/or exteriorly disposed non-wooden materials. Such composite bats, however, are not uniformly accepted by all leagues, for example Major League Baseball®. Further, the use of exteriorly disposed non-wooden materials may disrupt the natural wood finish more commonly associated with game of baseball.
Thus, there is a need in the art for an improved wooden baseball bat having enhanced reinforcement properties, but without substantially altering the function and/or the aesthetic view of the traditional wooden baseball bat.